Multiscale Crystal Plasticity Modeling for Metals

Title: Algorithms and Implementation for the Concurrent Atomistic-Continuum Method.

Abstract: Unlikemany other multiscale methods, the concurrent atomistic-continuum
(CAC) method admits the migration of dislocations and intrinsic
stacking faults through a lattice while employing an underlying
interatomic potential as the only constitutive relation. Here, we
build algorithms and develop a new CAC code which runs in parallel
using MPI with a domain decomposition algorithm. New features of the
code include, but are not limited to: (i) both dynamic and
quasistatic CAC simulations are available, (ii) mesh refinement
schemes for both dynamic fracture and curved dislocation migration
are implemented, and (iii) integration points in individual finite
elements are shared among multiple processors to minimize the amount
of data communication. The CAC program is then employed to study a
series of metal plasticity problems in which both dislocation core
effects at the nanoscale and the long range stress field of
dislocations at the submicron scales are preserved. Applications
using the new code include dislocation multiplication from Frank-Read
sources, dislocation/void interactions, and dislocation/grain
boundary interactions.

Crystal
plasticity modeling is useful for considering the influence of
anisotropy of elastic and plastic deformation on local and global
responses in crystals and polycrystals. Modern crystal plasticity
has numerous manifestations, including bottom-up models based on
adaptive quasi-continuum and concurrent atomistic-continuum methods
in addition to discrete dislocation dynamics and continuum crystal
plasticity. Some key gaps in mesoscale crystal plasticity models will
be discussed, including interface slip transfer, grain subdivision in
large deformation, shock wave propagation in heterogeneous
polycrystals, and dislocation dynamics with explicit treatment of
waves. Given the mesoscopic character of these phenomena, contrasts
are drawn between bottom-up (e.g., atomistic and discrete dislocation
simulations and in situ experimental observations) and top-down
(e.g., experimental) information in assembling mesoscale constitutive
relations and informing their parameters.